integration-tests/flakes: Eliminate slow nixpkgs copy

integration-tests/flakes/default.nix

@@ -14,11 +14,10 @@ in tools.makeTest {
   testScript = ''
     import re
 
-    deployer.succeed("sed -i \"s @nixpkgs@ $(readlink /nixpkgs) g\" /tmp/bundle/flake.nix")
+    deployer.succeed("sed -i 's @nixpkgs@ path:${pkgs._inputs.nixpkgs.outPath}?narHash=${pkgs._inputs.nixpkgs.narHash} g' /tmp/bundle/flake.nix")
 
     with subtest("Lock flake dependencies"):
-        # --impure required for path:/nixpkgs which is a symlink to a store path
+        deployer.succeed("cd /tmp/bundle && nix --experimental-features \"nix-command flakes\" flake lock")
-        deployer.succeed("cd /tmp/bundle && nix --experimental-features \"nix-command flakes\" flake lock --impure")
 
     with subtest("Deploy with a plain flake without git"):
         deployer.succeed("cd /tmp/bundle && ${tools.colmenaExec} apply --on @target --evaluator ${evaluator}")

integration-tests/flakes/flake.nix

@@ -2,7 +2,7 @@
   description = "A simple deployment";
 
   inputs = {
-    nixpkgs.url = "path:@nixpkgs@";
+    nixpkgs.url = "@nixpkgs@";
   };
 
   outputs = { self, nixpkgs }: let

integration-tests/nixpkgs-stable.nix

@@ -4,5 +4,10 @@ in import flake.inputs.stable.outPath {
   overlays = [
     flake._evalJobsOverlay
     flake.overlay
+
+    # Pass through original flake inputs
+    (final: prev: {
+      _inputs = flake.inputs;
+    })
   ];
 }

integration-tests/nixpkgs.nix

@@ -4,5 +4,10 @@ in import flake.inputs.nixpkgs.outPath {
   overlays = [
     flake._evalJobsOverlay
     flake.overlay
+
+    # Pass through original flake inputs
+    (final: prev: {
+      _inputs = flake.inputs;
+    })
   ];
 }

integration-tests/tools.nix

@@ -38,11 +38,15 @@ let
     # We include the input closure of a prebuilt system profile
     # so it can build system profiles for the targets without
     # network access.
-    deployerConfig = { lib, config, ... }: {
+    deployerConfig = { pkgs, lib, config, ... }: {
       imports = [
         extraDeployerConfig
       ];
 
+      nix.registry = lib.mkIf (pkgs ? _inputs) {
+        nixpkgs.flake = pkgs._inputs.nixpkgs;
+      };
+
       nix.nixPath = [
         "nixpkgs=${pkgs.path}"
       ];